Luna/apps/sh.cpp

#include <luna/Vector.h>
#include <os/ArgumentParser.h>

#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>

static Result<Vector<char*>> split_command_into_argv(const char* cmd)
{
    char* str = strdup(cmd);

    Vector<char*> result;

    char* segment = strtok(str, " \n");
    TRY(result.try_append(segment));

    if (segment == NULL) return result;

    for (;;)
    {
        segment = strtok(NULL, " \n");
        TRY(result.try_append(segment));

        if (segment == NULL) return result;
    }

    return result;
}

[[noreturn]] static void execute_command(const char* command)
{
    Vector<char*> argv;
    bool ok = split_command_into_argv(command).try_move_value_or_error(argv, errno);
    if (!ok)
    {
        perror("failed to parse command");
        exit(1);
    }

    if (argv[0] == NULL) exit(0);
    execvp(argv[0], argv.data());
    perror(argv[0]);
    exit(1);
}

Result<int> luna_main(int argc, char** argv)
{
    StringView file;
    StringView command;

    FILE* f;

    os::ArgumentParser parser;
    parser.add_positional_argument(file, "file"_sv, "-"_sv);
    parser.add_value_argument(command, 'c', "command"_sv, true);
    parser.parse(argc, argv);

    if (!command.is_empty()) { execute_command(command.chars()); }

    if (file == "-") f = stdin;
    else
    {
        f = fopen(file.chars(), "r");
        if (!f)
        {
            perror("fopen");
            return 1;
        }
    }

    while (1)
    {
        if (file == "-")
        {
            char* cwd = getcwd(NULL, 0);
            if (!cwd)
            {
                perror("getcwd");
                return 1;
            }
            printf("sh %s%c ", cwd, getuid() == 0 ? '#' : '$');
            free(cwd);
        }

        char cmd[4096];
        char* rc = fgets(cmd, sizeof(cmd), f);
        if (!rc) return 0;

        if (strspn(cmd, " \n") == strlen(cmd)) continue;

        pid_t child = fork();
        if (child < 0)
        {
            perror("fork");
            return 1;
        }

        if (child == 0) { execute_command(cmd); }

        if (waitpid(child, NULL, 0) < 0)
        {
            perror("waitpid");
            return 1;
        }
    }
}